3hkk

Human leukotriene C4 synthase (LTC4S) is an integral membrane protein that catalyzes the biosynthesis of leukotrienes, which have implications in the mediation of immediate hypersensitivity and inflammatory conditions, such as asthma and allergic rhinitis. The main function of LTC4S is the conjugation of an epoxide intermediate (LTA4) to reduced glutathione to form a proinflammatory mediator, LTC4, a peptidoleukotriene that mediates an inflammatory response characteristic of asthma attacks.

Structure of LTC4S (3HKK)
The structure of human leukotriene C4 synthase in a complex with glutathione sulfonate is shown at the left. LTC4S has a single chain with three transmembrane domains, and the crystallized structure 3HKK has sequence from http://en.wikipedia.org/wiki/Homo_sapiens Homo sapiens]. Full crystallographic information is available from OCA.

The gene for LTC4S is found on chromosome 5q35.

LTC4S Activity
Leukotriene C4 synthase is a unique membrane-bound enzyme that catalyzes the committed step in the biosynthesis of all the peptidoleukotrienes, also known as cysteinyl leukotrienes because of the presence of cysteine in their structures. The cysteinyl leukotrienes make up the slow-reacting substance of anaphylaxis (SRS-A).

Specifically, LTC4S conjugates reduced glutathione with the unstable epoxide LTA4 to form LTC4, making it a member of the glutathione S-transferase multigene family. Unlike other members of this family, however, LTC4S is not involved in cellular detoxification at all, and instead seems to be exclusively committed to the biosynthesis of LTC4.